:root {
  --bg: #f4f7fb;
  --bg-alt: #eef4ff;
  --card: #ffffff;
  --text: #0b1220;
  --muted: #4a607b;
  --primary: #2563eb;
  --primary-soft: #dfeafe;
  --border: #dbe5f2;
  --border-strong: #c4d2e8;
  --shadow: 0 12px 32px rgba(15, 23, 42, 0.08);
  --shadow-hover: 0 20px 40px rgba(15, 23, 42, 0.12);
  --radius: 16px;
  --transition: 0.2s ease;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  scroll-behavior: smooth;
}

a {
  color: inherit;
  text-decoration: none;
}

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.container {
  width: min(1120px, 92%);
  margin: 0 auto;
}

.header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: color-mix(in srgb, var(--bg), transparent 4%);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 68px;
  gap: 16px;
}

.brand {
  font-weight: 700;
  letter-spacing: 0.2px;
  font-size: 17px;
}

.nav-list {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: 8px;
  font-size: 14px;
  color: var(--muted);
}

.nav-list a {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  padding: 8px 12px;
  transition: color var(--transition), background var(--transition);
}

.nav-list a:hover {
  color: var(--primary);
  background: var(--primary-soft);
}

.nav-list a.active {
  color: var(--primary);
  font-weight: 600;
  background: var(--primary-soft);
}

.theme-toggle {
  border: 1px solid var(--border);
  background: var(--card);
  width: 40px;
  height: 40px;
  border-radius: 999px;
  cursor: pointer;
  transition: transform var(--transition), border-color var(--transition), box-shadow var(--transition);
}

.theme-toggle:hover {
  transform: translateY(-1px);
  border-color: var(--border-strong);
  box-shadow: 0 8px 18px rgba(37, 99, 235, 0.16);
}

.hero {
  padding: 78px 0 56px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: -140px -120px auto auto;
  width: 340px;
  height: 340px;
  background: radial-gradient(circle, color-mix(in srgb, var(--primary), #ffffff 70%), transparent 65%);
  opacity: 0.5;
  pointer-events: none;
}

.hero-content {
  max-width: 800px;
}

.badge {
  display: inline-block;
  background: var(--primary-soft);
  color: #1e40af;
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 13px;
  margin-bottom: 16px;
}

h1 {
  font-size: clamp(30px, 5vw, 48px);
  line-height: 1.15;
  margin: 0 0 18px;
  letter-spacing: -0.02em;
}

.hero-desc {
  color: var(--muted);
  font-size: 18px;
  line-height: 1.75;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 24px;
}

.btn {
  padding: 11px 18px;
  border-radius: 12px;
  font-weight: 600;
  font-size: 14px;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.btn-primary {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 10px 18px rgba(37, 99, 235, 0.28);
}

.btn-secondary {
  background: var(--card);
  border: 1px solid var(--border);
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary:hover {
  box-shadow: 0 14px 22px rgba(37, 99, 235, 0.34);
}

.btn-secondary:hover {
  border-color: var(--border-strong);
}

.section {
  padding: 56px 0;
}

.section.alt {
  background: var(--bg-alt);
}

.section h2 {
  margin-top: 0;
  margin-bottom: 18px;
  font-size: clamp(26px, 4vw, 34px);
  letter-spacing: -0.01em;
}

.page-title {
  margin-top: 0;
  margin-bottom: 18px;
  font-size: clamp(28px, 4vw, 40px);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.section-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.grid {
  display: grid;
  gap: 18px;
}

.grid.two {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.grid.three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-hover);
  border-color: var(--border-strong);
}

.card h3 {
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 21px;
  line-height: 1.4;
}

.card p {
  color: var(--muted);
  margin: 0 0 12px;
  line-height: 1.75;
}

.meta {
  color: var(--muted);
  font-size: 13px;
  margin: 0 0 8px;
}

.list {
  margin: 0;
  padding-left: 18px;
  line-height: 1.8;
  color: var(--muted);
}

.text-link {
  color: var(--primary);
  font-weight: 600;
  transition: color var(--transition), opacity var(--transition);
}

.text-link:hover {
  opacity: 0.82;
}

.filters {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.chip {
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--muted);
  border-radius: 999px;
  padding: 7px 12px;
  font-size: 13px;
  cursor: pointer;
  transition: color var(--transition), background var(--transition), border-color var(--transition), transform var(--transition);
}

.chip.active {
  color: #fff;
  background: var(--primary);
  border-color: var(--primary);
}

.chip:hover {
  border-color: var(--border-strong);
  transform: translateY(-1px);
}

.timeline {
  display: grid;
  gap: 14px;
}

.timeline-item {
  border-left: 4px solid var(--primary);
  background: var(--card);
  border-radius: 10px;
  padding: 16px 18px;
}

.article {
  max-width: 820px;
}

.article h1 {
  font-size: clamp(30px, 4.5vw, 44px);
  margin-bottom: 14px;
}

.article h2 {
  margin-top: 30px;
  margin-bottom: 12px;
  font-size: 25px;
  line-height: 1.35;
}

.article p {
  color: var(--muted);
  line-height: 1.8;
}

.article .list {
  margin: 8px 0 2px;
}

.topic-card {
  min-height: 188px;
}

.footer {
  border-top: 1px solid var(--border);
  padding: 26px 0;
  color: var(--muted);
  font-size: 14px;
}

.footer .container {
  text-align: center;
}

.footer p {
  margin: 4px 0;
}

.footer a {
  color: inherit;
  border-bottom: 1px dashed color-mix(in srgb, var(--muted), transparent 35%);
}

.footer a:hover {
  color: var(--primary);
  border-bottom-color: color-mix(in srgb, var(--primary), transparent 30%);
}

[data-theme="dark"] {
  --bg: #020617;
  --bg-alt: #111b30;
  --card: #0f172a;
  --text: #e7eefb;
  --muted: #9baec9;
  --primary: #3b82f6;
  --primary-soft: #142747;
  --border: #1e2e48;
  --border-strong: #304565;
  --shadow: 0 12px 34px rgba(2, 6, 23, 0.52);
  --shadow-hover: 0 20px 40px rgba(2, 6, 23, 0.65);
}

@media (max-width: 900px) {
  .grid.two,
  .grid.three {
    grid-template-columns: 1fr;
  }

  .nav {
    flex-wrap: wrap;
    justify-content: center;
    padding: 10px 0 12px;
  }
}

@media (max-width: 560px) {
  .nav-list {
    width: 100%;
    justify-content: center;
    flex-wrap: wrap;
    gap: 10px;
    font-size: 13px;
  }

  .hero {
    padding-top: 56px;
  }
}